devil's advo - radiant vs scorched

jp_2

yep, if you wait long enough the room will be the same temperature throughout.

but will the milk return to white?

[Deleted User]

devil's advo - radiant vs scorched

in 'how come', dan states; .......the floor becomes a large 'radiator'...........warm ceilings, walls, and furniture........these objects become warm, you experience less heat loss because you're standing next to warm things.

accounting for the 'coolness' of moving air, doesn't the same thing happen, warm objects/less heat loss, with all heating systems?

jp_2

coolness of moving air

apparently, you have never been in a hot suana?

that seems to be a myth of hot water guys, FHA blows cool unfriendly air.

[Deleted User]

never been in a hot suana?

huh? sure i have, but that's 'live' steam

"that seems to be a myth of hot water guys, FHA blows cool unfriendly air" ya lost me there

Unknown

It *can* happen in *some* heating systems in *some* houses.

Radiant heats objects directly, quickly. It most effectively and evenly heats up objects. This helps with comfort.

Air-based systems don't heat objects directly. They heat air, which then has a tendency to rise, and is a less effective way to heat an object in the first place. By "less effective", that means it takes longer to give up X amount of heat to an object, which has a similar heat loss either way, so in effect the surface temperature of that object will TYPICALLY be lower with a hot air system than with a radiant system.

furthermore, since warm air rises, you are most effectively raising your ceiling temp first, and least effectively addressing your floor temperature. At least with baseboard you are fairly evenly addressing the cold wall over the BB units... with FHA you don't even have that.

HOWEVER... if your shell is insulated well enough, the FHA can be operated at low temps, so it doesn't rise as much, and with a lower heat loss the inside surface of the walls can receive heat from the air system much more effectively.

ALSO, if you don't use setback, you maximize your air system's ability to "charge" the objects with heat, instead of letting them all cool down at night, then trying to raise their temperature in a mad rush in the morning.

Basically, in a consistent temperature situation in a very well insulated home (and that means much better than "code minimum"), FHA can achieve good comfort if it's properly designed.

But none of things are generally present in most homes using FHA

Unknown

we call it "scorched hot dust", not "cool unfriendly air"

[Deleted User]

Radiant heats objects directly, quickly?

the legs on my couch/chairs, that have a 1sqin surface in contact with the floor, are being heated all the way up to the seating surfaces? mmmmm.........

jp_2

warm air rises

gotta disagree Rob. I think this all started with radiators and baseboards, hot ceilings that is.

FHA, F= forced, not gravity as in hot water systems.

I've measured less than 3F difference floor to ceiling in FHA systems. you "force" the air around with greater "force" than gravity, making temps even out.

put ice cubes in hot water and mix with a big spoon, you won;t find warm on top and cold on bottom.

jp_2

not steam

you will be burned with steam. 220F normally

Unknown

sure, if you put in a ceiling fan, or run the FHA at all times. as soon as you stop "mixing", it stratifies. Or, I suppose, if you have poor ceiling insulation you'll cool down that peak temp enough to run a natural convection loop at real power.

Moving the air does cause wind chill though, causing you to have to raise the temperature to compensate for an *equal* level of thermal comfort.

with today's modulating furnaces, you might be able to minimize the stratification though, you're right. You're still left with a less effective heat transfer method to heat up the surfaces of the room though, which... again.. is not necessarily not achievable, but it IS only achievable with a better envelope or a higher temperature to an equal level as a radiant system.

Unknown

those are heated by conduction, sure, but the RADIANT heat transfer is what is more effective than heating air, then air trying to impart that heat to another object.

That is... it radiates heat energy directly to objects through space. Thus the name, "Radiant Heat"

So you are radiating to the full surface of the object that can "see" the floor. After that, it's about conduction from bottom to top surface. And conduction is always king, but radiation is still much more effective than convection if the name of your game is to impart heat to an object, provided distances are reasonable.

[Deleted User]

not steam in that sense

'steam' in the sense of so much moisture in the air from pouring water on hot rocks 'steam'

[Deleted User]

yikes! jp

gravity makes cool air fall? and anti-gravity makes hot air rise?

jp_2

even dry

before the pouring of the rocks, fan air around, its darn hot!

also interesting to watch suana room temp DROP when adding water, I've seen it go from 150F to around 130F, but boy does it get hot.....

[Deleted User]

critical radiating distance?

now i'm following ya

but even if warming the objects takes a little longer/less efficient with forced air, is there such a dramatic diff that, let's say, you walked a potential customer through a house with radiant vs forced air/heat pump whatever, would they be sold on radiant? if they felt no diff, but you showed them the t-stats and the radiant read 68deg, but the forced air read 72deg, would the efficiency, less costly/year sell them?

[Deleted User]

its darn hot!

well sure it is, it's 150degs. and it's generally radiant of some sort

jp_2

hold your horses there rob

once "mixed", you can not separate. once hot and cold water mix, you can not "easily" separate back into hot and cold.

try separating chocolate from milk after mixed.

jp_2

what?

don't understand mike? please explain.

[Deleted User]

you posted

I've measured less than 3F difference floor to ceiling in FHA systems. you "force" the air around with greater "force" than gravity, making temps even out.

and i zoomed in on the, greater "force" than gravity, statement, and i wondered aloud about gravity causing cool air to fall. and if that was the case, then anti-gravity would be the causation for hot air to rise

jp_2

I see now.

gravity does cause cold air to fall, as it also causes warmer air to rise, same thing, same rule.

"greater force than gravity"; same principle applies when a furnace is in an attic, it will force hot air down. or an air conditioner in the basement that pushed cold air to the second floor.

if the fans were not strong enough, they could not over come the tendencies of the hot air to rise and the cold air to sink.

bill nye_3

Force

Why would you want to force anything? That "force" is what can make you feel uncomfortable. The more you force it the more you feel it and hear it.

The air movement is perceptable to the skin. True comfort is when you are not aware of the wind noise from "forced" hot air, or air movement.

with infloor radiant heat you don't hear it or feel it (if done properly) you just are very comfortable. You are not thinking hot or cold. You may not even be aware it is "just right".

It is hard to explain to some one who has not lived with radiant heat with proper controls. It is like that "perfect" summer night when you are cruising in your favorite car with all the windows open and you are not cold. Just right. Better in an Oldsmobile but whatever you have will have to do.

jp_2

force

""Why would you want to force anything?"""

well lets see how well the infloor works without forcing water...

just kidding..........without force we'd just be dust.

[Deleted User]

what?!

gravity does cause cold air to fall, as it also causes warmer air to rise, same thing, same rule.

i'm finding that hard to believe. please point me in the direction of the science book where that is stated?

bill nye_3

force

Yeah, I left myself open for that. When you force the water through the pipe hopefully you can not hear it from the living area. When you force the air into the room it can become objectionable.

I have lived with both in my home, I am much more comfortable with radiant heat.

jp_2

general laws

you will not find that statement anywhere that I am aware of, I'm just using a general law.

how could warmer air rise without colder air falling?

you would end up with a pressure imbalance. the ceiling air would have high air pressure and the floor would have low pressure.


it all has to balance out. they both follow the law of boyuancy I think.

also, without gravity, hot air will not rise.

added: look up convection in any begining physics book

also: this has to do with newtons law of gravity, kinetic energy, the gas laws, and some others i would guess...

jp_2

I agree

[Deleted User]

i see what you're saying

about the balance and all, but i'm pretty sure that gravity doesn't have anything to do with air movement

and while hot air is less dense than cold air, density/
weight has nothing to do with falling, because all objects, 10lbs or 1000lbs, fall at the same speed, and like their weight, their temp has no bearing on it

if we filled two identical balls to 12psi, and weighed one in a refrigerator and one in a sauna, would the cold ball weigh more. something inside me says 'no'

unless of course, it's an anomaly like water; as in, it expands when cooled vs contracting like other materials. and as of my last reading, scientists don't completely understand that, but theorize that it has something to do with the hydrogen bonding

jp_2

start here

read up on convection, its all about gravity.

you are mixing things up on density, remember hot air ballons.

take a jar partially full of corks and marbles, shake it up and see where the corks and marbles end up. have them about the same size.

corks = low density warm air

marbles= high density cold air

gravity starts to fall part when 'things' get real small and very light(not heavy), ask, Einstien. air is one thing that starts to fall apart. other forces become stronger than gravitational forces.

you are right, both the balls would weigh the same, but their volume or density would be different.

jp_2

look here:

Physics page

[Deleted User]

i don't know man

nothing personal, but i'm still not buyin it having to do with the gravitational effect upon air. again, something inside me says 'no'

where's an astronaut when ya need one? as in, when they're in 0 gravity, does the heated or cooled air just lay where it's generated or does it convect on it's own?

Unknown

efficiency can be had many ways, radiant is not the only game in town there.

but generally speaking the "WOW I'M COMFORTABLE" factor is what sells radiant. and unless the house is superinsulated, yes, they are likely to notice the difference. Superinsulated... maybe.

of course everything depends on how good each system you compare is, too. a poor radiant system is not necessarily better than a top of the line FHA system.

Unknown

easy, just wait. chocolate settles to the bottom.

or are you insinuating that no air cools down in the room and falls to the floor?

If so, your envelope rocks.

Tom Manton

dense

Gravity acts on objects of greater and lesser density. Cold air has a greater density, thus weighs more in gravity.

You could liquify air in outer space and it would still be weightless,why? No gravity.

All I know is that my radiant heated house, the heat is seemless, you don't hear it, you don't feel it, there are no temp swings, you just are comfortable.

Try putting your hand out a car window on a 100F day, you are sweltering inside, but your hand feels cooler, air passing over your skin liberates moisture, evaporative cooling. Same principle applies to scorched air, air is moving, percieved comfort level is lower.

Radiant heats with infrared, long wave (heat) is not released until it strikes an object (furniture, walls ceiling, people)
Besides I like my warm floors, FHA has a tough time heating floors.

[Deleted User]

FHA has a tough time heating floors

unless we do it like the romans, but with a furnace or heat pump

Gordy

Simple as the solar system

For billions of years the sun has radiated at 10,000* heating the earth 92,000,000 miles away, and all molecules in between, and beyond. When the day turns to night the ground, and all objects heated radiate that heat back to space. Radiant heat has always been with us, and always will be. Its as simple as nature. Someone, or something else thought it was the best way to heat.

gordy

[Deleted User]

which is why

passive solar is my interest of late, and have tentative plans for my next house

Maine Doug_70

But the ball

in the fridge will not stay at 12 PSI. To keep it at 12 PSI you have to add more air thus making the ball in the fridge heavier. Can you measure pressure differentials in the air in a room from floor to ceiling? Are they because the air is denser when cold and gravity pulls it towards the floor?

Tom Blackwell_2

I just have to say this! Just came in from my shop with radiant floor. Floor temperature is 70 degrees, air temperature is 58 degrees, and I was quite comfortable with a short sleeve shirt on. Air temperature would have to be 70+ for the same comfort level. Nuff said...

Maine Doug_70

If I ever get

to do another home, I think I will do both. I have radiant and panel rads and a wall mounted split unit for AC now in the Maine place. Heat is from twin Biasi boilers so I have a completely redundant system except for power source.

I would install a full HVAC system since the heating part of the system can be gas or oil and once you have the ducts in for AC one might as well make it a furnace too. The radiant and panel rads would be the normal method for heating. The furnace would be backup and for quick warmup when the temp had been setback while away for more than a couple of days.

I would like to have a power backup system also since the power from electric companies is getting less reliable.

Another option would be a brand new steam system that required no electric source if I am still in Steamhead's territory.

Gordy

The cheapest

and the easiest of solar heatng to incorporate into a dwelling.

Gordy

jp_2

not personal

mike,

you are welcome to disagree here. if science was so easily understood we'll all be Einsteins, things aren't always as they seem.

what is your theory as to way air moves?

Heres one: the space stations appears to be in zero gravity, gravity there is actually only 10% less than on earth, they happen to be falling back to earth at a great speed, like on the vomit comet!

Did you read up on convection?